Shabbat 138 - Straining wine
Rabbi Eliezer is known for allowing to prepare for a mitzvah on Shabbat. Since enjoying wine is a mitzvah, Rabbi Eliezer allows to pour wine into a strainer, if it was set up before Shabbat. Setting it up in the first place would be prohibited though, either because he is building a temporary tent, or because it is too similar to his weekdays activities.
The Sages do not allow preparing for a mitzvah on Shabbat and therefore do not permit straining the wine. What if he violated the law and strained wine on Shabbat? Rabbah says that he is doing the prohibited labor of selecting (removing the dregs), while Rav Zeira says that he is liable for doing sifting. As a result of this disagreement, the court cannot stop him, because the witnesses would need to give a clear unambiguous explanation of the prohibition, and here they can't; however, if he did it by mistake, he will have to bring a sacrifice whichever reason applies.
Rav said that in the future the Torah will be forgotten from Israel, following the prophecy that " God will make extraordinary things, and the wisdom of the wise will perish ." "Extraordinary" refers to Torah. But why should this be? If they forget the laws - let them learn the basics rulings, and if they forget the reasons - let them learn the Talmud! The answer is that the uncertainties like the above will plague them.
Rabbi Shimon said, "God forbid! The Torah will not be forgotten. Rather, there will not be a clear law ("Mishnah Berurah" in Hebrew) to follow, and everybody will have his own opinion on which law to correct."
Art: Giacomo Francesco Cipper - A Peasant Pouring A Glass Of Wine